This invention relates generally to apparatus for detecting the presence of sound and more particularly, but not by way of limitation, to sound detecting apparatus which interrupt a program to which a person is listening for the purpose of notifying such person of the detected sound.
The following statement is intended to be a prior art statement in compliance with the guidance and requirements of 37 C.F.R. Sers. 1.56, 1.97 and 1.98.
U.S. Pat. No. 3,471,846 issued to Cotter et al proposes a sound responsive intruder detection circuit which utilizes two channels, a main channel and a cancel channel, to detect the presence of sound. The two channels are to be used to differentiate between "friendly" and "unfriendly" sounds. When an unfriendly sound is detected, the proposed device is to activate an alarm relay.
U.S. Pat. No. 3,984,803 issued to Hawk et al proposes a seismic intrusion detector system which is to include means for generating an electrical signal in response to seismic movement of the generating means, a bandpass amplifier coupled to the generating means, a threshold detector means for passing signals from the amplifier exceeding a preselected voltage level, means for counting and storing the signals, variable frequency oscillator means for generating and transmitting on demand an audio signal representing the number of man-associated seismic movements detected by the device, and means for monitoring the audio signal.
U.S. Pat. No. 4,091,366 issued to Lavallee discloses a sonic monitoring method and apparatus. The apparatus is proposed to include microphones for picking up sounds, discriminators for generating alarm signals when the power of the amplified input from the microphones exceeds a predetermined level, timers for generating predetermined timing signals responsive to the generation of the alarm signal, switches which are activated when an alarm signal is detected, and an audio output.
U.S. Pat. No. 3,719,891 issued to Lee proposes still another type of sound detection system.
From these references it is apparent there is a need for an alarm device which detects the presence of sound. However, there is also the need for such a device to have a relatively simple design and construction so that it may be more easily manufactured and maintained. Furthermore, there is the need for a device which can detect a sound and then interrupt a program which a person is perceiving so that the person can be notified of the sound. In this way, the person is made aware of sounds which are external to the perceived program and of which the person would otherwise be unaware.
Although each of these references proposes a type of sound detection and alarm device, it is believed that these references fail to disclose such a device having a relatively simple design which enhances the ease of manufacture and maintenance thereof. It is further believed that these cited references fail to propose a system for interrupting a program to which a person is listening when a sound is detected and for audibly presenting the detected sound to the listener during the interruption. In particular, it is believed that the cited references fail to propose an apparatus which interrupts a program to which a person is listening on a set of earphones and presents the detected sound to the listener through the earphones.